This pamphlet is designed to point out potential problems related to indoor air quality, review steps that building owners and managers can take to investigate and correct problems, and assist in obtaining additional help with indoor air quality issues.


Over the past 40 years, a revolution has taken place in building design and construction. Modern buildings have been compared to spaceships, with self-contained ventilation systems designed to provide a closely controlled environment that created nearly optimum conditions for most occupants.

Then came the "energy crisis". To reduce energy costs, buildings were better insulated and computerized controls were added to reduce the use of heated air during non-use hours. At the same time, synthetic components replaced traditional natural building materials. Buildings "sealed" or insulated to preserve conditioned air also preserved and concentrated the air contaminants released by building components and operations. The ventilation systems also became breeding grounds for microorganisms. Both air contaminants and microorganisms were recirculated throughout the building.

As the work force shifts from manufacturing to the service industries, "indoor air pollution" and "sick building syndrome" have become concerns for an increasing number of employees. Building owners and managers are being challenged to respond to these concerns.

What Are the Problems?

The National Institute of Occupational Safety and Health (NIOSH) reports that several factors contribute to poor indoor air quality. They include inadequate ventilation, air contaminants from inside the building, air contaminants from outside the building, microbial contamination, contamination from the building fabric, and other unknown causes.

  • Thermal Environment. When many occupants complain about poor indoor air quality or "stuffiness", they actually may be referring to comfort conditions such as temperature or relative humidity. For example, warm, dry air in winter may elicit symptoms of dry throat, coughs, or upper respiratory irritation in much the same way as chemical or biological air contaminants.

Thermal comfort is dependent on many factors, including:


Activity levels

Air movement


Air temperature

  • Air Contaminants. These can be divided into two categories: particulate, which can include solids and fine droplets (mist), and gas and vapor.

Large particulate, which often comprise visible dust, usually is filtered by a person's respiratory system and often can lead to upper respiratory complaints. Smaller particulate, which often is invisible, can behave much like a gas and may be deposited in the lungs. Particles of concern include tobacco smoke, asbestos fibers, and business machine chemicals. Dusts in general often are referred to as nuisance dusts.

Gas and vapor can cause health effects in several ways. They may be upper or lower respiratory irritants or they may be absorbed into the bloodstream after respiration. They may affect various parts of the body, causing headaches, nausea, and dizziness. Gases of concern include carbon monoxide (CO) from combustion sources; formaldehyde from paneling, particle board, carpeting, and furniture; and volatile organic compounds (VOCs), the name for a wide variety of chemicals from such items as adhesives, carpets, furniture, and ceiling tiles.

  • Biological Contaminants. This group can be subdivided into allergens, which include fungi, spores, and insect parts and feces; and pathogens, bacteria and viruses, which normally are contained in or on particulate matter. Although many people are greatly concerned about exposure to pathogens such as Legionnella bacteria (which causes “Legionnaires disease”), these occurrences are very rare. In fact, many more people are affected by allergens and develop sensitivities after a period of exposure.

What to Do?

When confronted with an indoor air quality problem, the first reaction often is to "have the air tested" in order to determine what is causing the problem. However, air monitoring is expensive, and the results may be inconclusive for several reasons. First, air contaminants often are found in very low levels. Second, the effect of these contaminants in an office environment may be due to the combined (synergistic) effects of two or more contaminants. Third, the effects of biological contaminants cannot be correlated to exposure levels. In short, many microorganisms are very common species. The fact that they are detected in a building does not necessarily mean they are causing harm.

If air monitoring is not recommended, then what should be done? Several steps can be taken to improve indoor air quality.

First, comfort conditions, the thermal environment discussed previously, can be addressed by ensuring recommended temperature and humidity levels. Recommended temperature ranges are 68 to 76 degrees in winter, and 74 to 80 degrees in summer. Relative humidity should be maintained within a range of 30% to 60%. Maintaining conditions within these ranges may eliminate complaints without the necessity of taking other action.

The most important step, however, is to ensure that building ventilation is as effective as possible. Because symptoms often are related to a gradual buildup of several air contaminants, one effective remedy is to dilute these unwanted contaminants with outdoor air. Many ventilation systems include outside air intakes. However, in an attempt to reduce energy costs, these intakes may be partially or fully closed. Adjusting the supply of outdoor air to recommended levels (15-20 cubic feet per minute, per occupant, for most office areas) may be the most effective step in improving indoor air quality. A qualified person should do such adjustments. In some cases, this may require the expertise of a ventilation engineer.

The next step is to ensure that air is circulated uniformly throughout the entire building. Recommended routine inspection and maintenance of the system also is very important. If building staff cannot perform these functions, a qualified service contractor should be consulted.

It also may be possible to reduce contaminants by eliminating sources within the building. Information on cleaning and maintenance products should be reviewed to ensure that the products are used properly and are not a source of odor or contaminants. It is not unusual to find business machines such as photocopiers in a small room with little or no ventilation, even when the manufacturer recommends "adequate" ventilation or even exhaust ventilation. Are building air intakes located near odor or contaminant sources such as bathroom vents, loading docks, trash containers or exhaust vents or stacks? If so, relocating the source of the contaminants may prove beneficial.

When investigating an indoor air quality problem, it is important to solicit information from building occupants. This can be done by questionnaires or by interviews. Remember to keep occupants informed of corrective actions taken. Some problems develop gradually. In the same way, corrections may produce only subtle improvements. Let occupants know what steps you are taking.

Can Problems Be Avoided?

From time to time, office interiors are renovated. Large rooms are subdivided. Open spaces are partitioned into smaller areas. With proper planning and coordination, some common pitfalls can be avoided.

When installing or removing walls or partitions, note existing ventilation ductwork and diffusers. Do these need to be relocated? Has hidden ductwork been disconnected during renovation? Can low odor products be used in place of odorous paints or adhesives? Are small renovation or maintenance jobs done while office workers are not present, and is ventilation left in operation overnight or during weekends to remove any solvent vapor, gas, or odor? Vendors of office furniture and accessories often can provide information on the release of formaldehyde or volatile organic compounds, especially for large quantity purchases.

By taking proper precautions during renovation and maintenance work, problems can be avoided.

Guides for Evaluating Indoor Air Quality

The following guides are designed to assist in evaluating and correcting problems related to indoor air quality.

Begin by completing the "Building Ventilation Assessment." Answer all appropriate questions. The information you gather here will prepare you for completing the "Building Walk-Through Survey", which may reveal problems relating to indoor air contaminants. The third guide, "Complaint Survey", is designed to assist you in obtaining information from building occupants.

These guides may assist in diagnosing problems and making necessary corrections. If you need additional assistance from an outside source, the information you have gathered will be valuable to the person you contact for assistance.

Additional help may be available from private consultants with experience in indoor air quality evaluation, or from MOSH Consultation Services (see Resourses, following).

Building Ventilation Assessment

It is important that the building manager or other designated person be knowledgeable about the operation of the building's ventilation system. The following information will be useful in evaluating indoor air quality problems. The time and effort used in obtaining the answers to these questions will be well spent. Note that not all of the following questions apply to all systems.

By researching and compiling this information, you should have a better understanding of how your ventilation system is designed to perform and whether or not it is performing as it was intended. You may identify areas that need improvement. If so, ensure that an experienced, well-qualified ventilation contractor is employed.

Building Characteristics

  • Building age ______
  • Number of floors ______
  • Type of windows (clear, tinted, etc.) ______

Do windows open? Yes  No

  • Who cleans the building interior? ______

How often? ______

  • What is the building layout? (i.e., open space, individual offices, combination)


  • Has the building been renovated?  Yes No

If Yes, when? ______

What changes were made? ______


  • Who is responsible for the building:

management ______

maintenance ______

ventilation (on-site or contractor) ______

Ventilation System

  • Heating system ______
  • Type of fuel ______
  • Type of heat (radiator, forced hot air, etc.)______
  • Air conditioning (central, zone, individual) ______

Layout and Operation of System

  • Central air handling units? Yes No
  • Area (zone) air handling units? Yes No
  • Individual (window) air handling units? Yes No
  • Plenum-type return air? Yes No
  • Ducted return air? Yes No
  • Return air at air handling unit? Yes No
  • Does unit provide continuous circulation? Yes No
  • Is system air volume constant? Yes No
  • Is system air volume variable? Yes No
  • Does computer control system? Yes No

If so, is performance monitored? Yes No

By whom? ______

How often? ______

  • Does system provide outside makeup air?  Yes No
  • Are makeup air controls:  manual automatic
  • Who inspects/adjusts makeup air controls? ______
  • How much make-up air is provided (CFM per person or % of makeup) ______


  • Do the following components receive routine inspection/maintenance?

Supply air outlets Yes No

Filters Yes No

Thermostats/sensors Yes No

Coil condensation pans Yes No

Internal duct work Yes No

Dampers Yes No

Belts Yes No

If so, by whom ______

Is system equipped with a humidifier? Yes No

If so, what type? ______

Can or do occupants adjust:

Supply air outlets Yes No

Thermostats Yes No

Other controls (list) Yes No


  • Are there operations/processes/machines that can produce air contaminants?

 Yes No

If so, list them ______

  • Was the ventilation system commissioned (tested on installation)?

 Yes No

  • Has the system ever been balanced or adjusted? Yes No

If yes, by whom ______

When ______

Is report available? Yes No

  • Is there a smoking policy? Yes No

Does it meet the requirements of MOSH regulations?  Yes No

  • Has the volume of air, per room occupant, been measured? Yes No

Note: The American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) currently recommends 15-20 cubic feet per minute (CFM), of outside air, per occupant, for most office or public building environments.

  • What is the efficiency of the filters for the ventilation system? ______


Note: Filters usually are installed to protect equipment, not to improve air quality. If not changed regularly, they slow the airflow and can become a source of contaminants. With the advice of a qualified person, filters can be upgraded to improve air quality.

Building Walk-Through Survey

In conducting a walk-through survey, be alert for four general sources of contaminants, in addition to ventilation system problems. These are:

  • chemical sources from within the building
  • chemical sources from outside the building
  • chemical sources from the building fabric itself
  • microbial contamination

Many people feel that the first response to an indoor air contaminant problem should be to conduct air monitoring. However, in many cases, the complaints of occupants may be a result of inadequate ventilation. Air monitoring often is unnecessary or non-conclusive because air contaminants may be present in levels too low to monitor, or the symptoms of exposure may be the result of the combined (synergistic) effects of contaminants. Also, improved ventilation may successfully bring relief from the effects of air contaminants without air monitoring.

In conducting your building walk-through survey, be aware that although occupants may refer to “poor air quality”, their complaints in fact may relate to other factors: thermal comfort (too hot, too dry), poor work station design (poor posture resulting in body aches), inadequate lighting (glare resulting in eye strain or headaches), or stress (job-related or personal).

The following questions highlight potential problem areas, which should be reviewed in your survey.

Ventilation System

  • Is each office space equipped with one or more air supply ducts? Sometimes, space is repartitioned and some rooms are left without ventilation sources.

 Yes No

  • Is air flowing from supply air ducts? Ducts may be disconnected above a dropped ceiling, air may not be flowing to the ends of a system or a fan may be broken.

 Yes No

  • Have occupants readjusted air outlets? Individual outlets may be opened or closed, thus upsetting the balance of a larger system.

 Yes No

  • Are return air grills kept open and clear? Boxes, cabinets, or other materials may block air grates, usually located near a mechanical room.

 Yes No

  • Are temperatures uniform throughout the building? The sun shining into windows may make one side of a building warmer. Occupants may have readjusted thermostats, or thermostats may need to be calibrated. Office partitions may keep heated/cooled air from circulating, producing different temperatures at ceiling and floor levels.

 Yes No

  • Are maintenance personnel properly trained to perform routine inspection and maintenance? On-site maintenance personnel may not be familiar with equipment and manufacturer's recommendations, such as how often to change filters or where filters are located.

 Yes No

Are routine inspections and maintenance performed?

 Yes No

Sources of Contaminants from Inside the Building

  • What equipment may be producing contaminants? Photocopiers, video machines and blueprint machines may release vapor or gas. The electrical components of these machines may produce ozone.




  • Are machines installed and operated according to manufacturer's specifications?

 Yes No

  • Are they in well-ventilated areas?

 Yes No

  • Is there an art department, photo lab, science lab, or storeroom? Many of these areas contain materials that are odorous, volatile, and spillable.

 Yes No

  • What cleaning products are used on a routine basis or in an emergency?



  • Are materials used properly in accordance with manufacturer's specifications? Products may be used in concentrations in excess of recommendations. Some products contain an objectionable odorant.

 Yes No

  • Are pesticides used for extermination?  Yes No
  • Is a commercial exterminator utilized? Yes No

In some cases, the pesticide is mixed with a "carrier" or solvent, which is volatile and odorous.

  • Can spraying be replaced by a monitoring program? Yes No
  • What materials do occupants bring in? ______


  • Are products such as cleaning supplies or room deodorizers used properly?

 Yes No


  • Is a chemical information list compiled, and are material safety data sheets (MSDS) available? Maryland law requires that all employers make a list of hazardous materials, and obtain a material safety data sheet for each substance. This information can be a valuable resource in determining what is used in a building.

 Yes No

  • Is there a designated smoking area in the building? Cigarette smoke is considered to be the largest contributor to poor indoor air quality.

 Yes No

  • Does the designated smoking area have a separate exhaust system? If not, smoke may be recirculated into non-smoking areas.

 Yes No

Note: MOSH regulations require that a designated smoking area have a separate ventilation system that exhausts directly to the outside without recirculating into non-smoking areas.

Sources of Contaminants from Outside the Building

  • Can outside contaminants be drawn into system air intakes? Inspect roof and outside walls to determine if building exhaust or other source of contaminants is near an air intake. Contamination sources can include exhaust vents (bathrooms, machines, labs), dumpsters, idling vehicles, and air pollution sources on adjoining property. Wind patterns can trap air contaminants on a flat roofed building, so that contaminants are held and drawn into the ventilation system. A higher exhaust stack may prevent re-entry into the building. A rule-of-thumb guide is that an exhaust stack should be 10 feet higher than an air intake located within 50 feet of the stack.

 Yes No

Sources of Chemical Contaminants from the Building Fabric

  • Have new furniture, carpets, or draperies been installed? These products can "off-gas" or release volatile organic compounds (VOCs) for weeks or months after installation.

 Yes No

  • Is painting, carpet installation, or other repair or renovation performed during periods of low occupancy? Paint solvents, carpet adhesives, and other chemicals used by contractors can be odorous and irritating. By working on weekends with maximum ventilation, or by substituting products, discomfort can be minimized.

 Yes No